Streptanthus petiolaris
Mem. Amer. Acad. Arts, n. s. 4: 7. 1849.
Annuals; pilose proximally, glabrous distally. Stems unbranched or branched distally, 2–12 dm. Basal leaves subrosulate; long-petiolate; blade lyrate-pinnatifid, oblanceolate in outline, 3–21 cm, margins (of lobes) dentate, (surfaces pilose). Cauline leaves (petiolate); blade lyrate-pinnatifid, hastate, or (distally) linear-lanceolate, 2–14 cm × 5–70 mm, margins (distally) entire. Racemes ebracteate, (lax). Fruiting pedicels divaricate to ascending, (straight or curved upward), 7–13 mm. Flowers: calyx subcampanulate; sepals lavender, (oblong), 3–4.5 mm, not keeled; petals white to lavender, 4–8 mm, blade 1.5–4 × 1.5–2 mm, margins not crisped, claw 2.5–4 mm, narrower than blade; stamens tetradynamous; filaments: median pairs (distinct), 2.5–4 mm, lateral pair 1.5–3 mm; anthers (all) fertile, 0.5–1 mm; gynophore 0.3–0.7 mm. Fruits suberect to divaricate-ascending, slightly torulose, straight, strongly flattened, 4–9 cm × 3.5–5 mm; valves each with obscure midvein; replum straight; ovules 28–50 per ovary; style 0.5–2.7 mm; stigma slightly 2-lobed. Seeds orbicular, 3.5–5 mm diam.; wing 0.8–1.4 mm wide, continuous. 2n = 28.
Phenology: Flowering Mar–May.
Habitat: Thickets, roadsides, canyons, grassy grounds, bluffs, knolls, rocky limestone prairies, juniper-oak woods
Discussion
Streptanthus petiolaris was treated by other North American authors under Arabis, but the species does not belong to that genus (I. A. Al-Shehbaz 2003b) or to Boechera; it has 2n = 28, a chromosome number universal in Streptanthus and not found in any species of Arabis or Boechera, and it lacks the branched trichomes characteristic of those genera.
Selected References
None.
Lower Taxa
"elongated" is not a number."thick" is not a number."dm" is not declared as a valid unit of measurement for this property.